Author: Phil Dodson, Kathie Owens, and Kathy Crooks
This inquiry activity uses an everyday item, soda, to help the students learn the concepts of solute and solvent and to review the components of a good experiment. The students will discuss and determine manipulated and responding variables and will write a hypothesis and procedure for part of the lesson. Throughout this lesson, the best teaching practices of inquiry approaches, hands-on/minds-on learning, applications to the real world will be emphasized.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
For the teacher demonstration:
For each student group:
Cost approximately $1.00 per person
This part of the lesson will be a teacher demonstration. The teacher needs one unopened small PET bottle of Coke and another small PET bottle of Coke that was uncapped two days ago. He/She will uncap the soda and place the balloons over the threads of each bottle. Shake each bottle to expel any carbon dioxide into the balloon. Have the class list and discuss their observations.
Assessment: The assessment should center on the discussion to help students realize that carbon dioxide is the dissolved gas in soda and by shaking it the gas is released from the liquid and goes into the balloon. When the soda is left open the dissolved carbon dioxide is released into the air (because the amount of carbon dioxide in the air is less than inside the bottle and this 'system' tries to reach equilibrium).
Give each group of students two bottles of different soda of the same size. Ask the students to write a hypothesis about the amount of carbon dioxide in each bottle of soda. Have the students write and follow a procedure to test their hypothesis.
Assessment: Check each group's procedure or discuss procedure as a class. Monitor the groups to see if they are following directions and working safely.
Students report their findings and their explanations of these findings to the class. Record student data to determine if there are any trends in the amount of carbon dioxide in different types of soda.
Ask the students for the manipulated and responding variables in this experiment. What was held constant? Why is this important?
Assessment: Have students discuss what would happen to the experiment if we changed two or more variables at the same time? For example, how would it affect the experiment if two different size bottles (2 Liter and 20 oz.) of two different brands (Coke and store brand) of soda were used?
Have the class predict the amount of gas obtained from larger quantities (2L bottles) of soda before the demonstration is performed. Test these hypotheses.
Assessment: Monitor the discussion of students' predictions and the results of the demonstration. Ask the students to define the manipulated and responding variable in each case.
Knowledge of general lab principles
General knowledge of lab safety
Common Core Standards:
Solubility is the measure of how well a solute (carbon dioxide) will dissolve in a solvent (soda) at a given temperature. Most solids dissolve better when the temperature of the solvent increases. This pattern is not true for gases, which become less soluble when the temperature goes up.
In a controlled experiment all factors (variables) are kept constant except for one (the manipulated variable). The factor that changes as a result of the manipulated variable is called the responding variable.
Science is characterized by exploration and explanation. Scientists "discover" that which can be directly observed and experienced. Science does not stop at exploration. Scientists look for patterns in their observations and propose explanations for their observations. Engaging students in the processes of building scientific knowledge by having them hypothesize, collect data, make observations, analyze their findings, and communicate their results helps them better understand the nature of science.
A solution is basically a combination of two things that distribute evenly throughout one another. The solute is the material that dissolves and the solvent is the substance, usually a liquid, that does the dissolving.
Do not drink the soft drinks after shaking them. Care must be exercised because the contents of the bottles are pressurized. Have towels available in case of spills. Goggles must be worn. If there is the possibility of latex allergy - use a grocery store produce bag and a rubber band instead of a balloon.
Students can discuss the components of a valid experiment and why they are important. Have students discuss how they could determine: which paper towels are most absorbent, which batteries last the longest, which bubble gum blows the biggest bubbles. Have students brainstorm other examples of common items that could be experimentally tested.
Ask the students to review the following experiment. Is it a fair test? If not, what could be done to further control variables?
Student X decided to determine which type of microwave popcorn left the least amount of kernels. He knew his mom had some old bags of popcorn in a cabinet, so he decided that this would be Type A. He then went to the grocery store and chose Type B and Type C. Type A was lite buttered popcorn, Type B was kettle corn and Type C was movie theater popcorn. The student popped the popcorn, poured it into separate bowls and threw away the bags. He then picked all the kernels out of bowls A & B and counted them. He began to pick the kernels out of bowl C when his cat ran through the kitchen and knocked bowl C off the counter. The student cleaned it up, counting all the kernels he could find. Based on his experiment, the student determined that Type A left the most kernels.
Grouping Suggestions: Whole class group for the engagement and elaboration; groups of 4 for the exploration and explanation.
Pacing/Suggested Time: Do the activities on two separate days to give the students time to think for reflection.